In many systems having two-phase flows, for example, in the petroleum and nuclear industries, there is a need at present for more efficient equipment for accurately determining the various parameters representing these two-phase flows, especially the rate of each one of their components.
There exist a number of conventional devices (one of which is shown in U.S. Pat. No. 3,934,471) which are applicable to the linear measurement of the rate of a mixed flow of gas and liquid phases. Devices of this type, however, give satisfactory results only in special cases such as in dilute mixtures where mimimal sliding or differential flow velocities exist between the two phases (low rates and nearly homogeneous flows). On the other hand, when the volumetric gas-liquid ratio exceeds a definite threshold, considerable sliding or slippage can occur between the two phases, which can result in inhomogeneous flows of various types: stratified, annular, or plug flows, for example. Variable pressure from the source of the flow, causing fluctuations in the separate flow velocities, exacerbates the difficulties encountered in accurate measurement. In cases like these, none of the existing devices is any longer capable of ensuring the accuracy required.
In order to overcome these difficulties, one often uses another technique, for instance when assessing the flow rate of a gas well. This technique consists of installing a separator on the outlet pipe of the well and measuring individually the rate of flow of each one of the phases. The main drawback of this method resides in the utilization of cumbersome and heavy equipment which is sometimes difficult to transport to well sites. Furthermore, the separators used at present for this type of measurement are not intended as a rule for a linear installation, and thus are not suitable for the continuous control of an individual well.